Parameter Editing

When the cursor is inside a helper function (not mainImage), the debug system generates a wrapper mainImage that calls the helper with configurable parameter values. The Parameters section appears in the debug panel to control how each parameter is populated.

Placeholder: debug-parameters.png — Parameters section showing a vec2 parameter in UV mode and a float parameter with a custom slider value.

Parameter Modes

Each parameter can be set to one of four modes:

UV

Maps the parameter from screen UV coordinates (0–1 range). The mapping depends on the parameter type:

Type	UV Expression
float	uv.x
vec2	uv
vec3	vec3(uv, 0.0)
vec4	vec4(uv, 0.0, 1.0)

This is the default mode for spatial parameters. It creates a gradient across the screen that lets you see how the function behaves across a range of inputs.

Centered UV

Aspect-ratio-corrected coordinates centered on the screen, ranging from approximately -1 to +1:

vec2 centeredUv = (fragCoord * 2.0 - iResolution.xy) / iResolution.y;

Type	Centered UV Expression
float	centeredUv.x
vec2	centeredUv
vec3	vec3(centeredUv, 0.0)
vec4	vec4(centeredUv, 0.0, 1.0)

Best for functions that expect centered coordinates, like distance fields or polar transformations.

Custom

Set a constant value using type-specific editors:

Type	Editor
float	Number input (step 0.01) + slider (0–1 range). Supports drag-scrub on the number input.
int	Number input (step 1). Supports drag-scrub.
bool	Checkbox toggle.
vec2	Per-component number inputs (X, Y). Each component can independently use a custom value or a preset.
vec3	Per-component number inputs (R, G, B) + color picker (hex input). Each component can independently use a custom value or a preset.
vec4	Per-component number inputs (X, Y, Z, W). Each component can independently use a custom value or a preset.
sampler2D	Channel dropdown: iChannel0, iChannel1, iChannel2, iChannel3.
User-defined struct	Inline expression editor (see below).

For unknown or user-defined struct types, a syntax-highlighted expression editor is shown instead of structured inputs. You can type any valid GLSL expression directly. The editor uses CodeJar for inline editing with syntax highlighting.

Preset

Use a built-in expression based on Shadertoy uniforms. Available presets depend on the parameter type:

float presets:

Preset	Expression
iTime	iTime
sin(iTime)	sin(iTime)
cos(iTime)	cos(iTime)
fract(iTime)	fract(iTime)
iTimeDelta	iTimeDelta

int presets:

Preset	Expression
iFrame	iFrame
int(iTime)	int(iTime)

bool presets:

Preset	Expression
iTime > 1.0	iTime > 1.0
iFrame > 30	iFrame > 30

vec2 presets:

Preset	Expression
uv	fragCoord.xy / iResolution.xy
uv centered	(fragCoord.xy * 2.0 - iResolution.xy) / iResolution.y
iMouse.xy/iResolution.xy	iMouse.xy / iResolution.xy
iResolution.xy	iResolution.xy

vec3 presets:

Preset	Expression
vec3(iTime)	vec3(iTime)
vec3(sin(iTime))	vec3(sin(iTime))

vec4 presets:

Preset	Expression
vec4(iTime)	vec4(iTime)
vec4(sin, cos, 0, 1)	vec4(sin(iTime), cos(iTime), 0.0, 1.0)

Component-Level Editing

For vector types (vec2, vec3, vec4), each component can be edited independently when in custom mode. Each component has its own mode toggle:

• Custom — enter a constant value
• Preset — use a component-level preset expression

Component Presets

Individual vector components can use these presets:

Preset	Expression
iTime	iTime
sin(iTime)	sin(iTime)
cos(iTime)	cos(iTime)
fract(iTime)	fract(iTime)
uv.x	uv.x
uv.y	uv.y

This lets you mix static and animated values in a single vector parameter. For example, you could set a vec3 color parameter to (sin(iTime), 0.5, uv.x) by using presets for the R and B components and a custom value for G.

Color Picker

For vec3 parameters, a color picker is available in custom mode. It displays a hex color input that syncs bidirectionally with the R, G, B component values. Editing the hex value updates the component inputs, and editing component values updates the hex display.

State Behavior

• Switching functions: Custom parameter values and modes are cleared when the cursor moves to a different function. This prevents stale overrides from one function being applied to another.
• Staying in a function: Parameter values persist as you move between lines within the same function.
• sampler2D parameters: The channel selector is always shown for sampler parameters regardless of mode, since textures can only be bound via iChannel0–3.